Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
Cash flows from operating activities:
Net income	$ 90,076	$ 98,061	$ 418,841	$ 223,566
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization			265,168	240,033
Amortization of discount on marketable securities			(4,862)	(10,869)
Amortization of discount and debt financing costs, net			3,973	1,726
Gain on sale of marketable securities			(33)	(498)
Provision for credit losses			97
Unrealized loss (gain) on equity securities recognized through income			1,073	(4,454)
Company's share of gain on the sales of co-investments			0	(870)
Earnings from co-investments			(38,554)	(32,365)
Operating distributions from co-investments			29,613	38,699
Accrued interest from notes and other receivables			(835)	(2,896)
Gain on the sale of real estate and land			(16,597)	0
Equity-based compensation			4,043	5,321
Loss (gain) on early retirement of debt, net	5,027	(332)	4,706	(1,668)
Gain on remeasurement of co-investment	0	0	(234,694)	(31,535)
Changes in operating assets and liabilities:
Prepaid expenses, receivables, operating lease right-of-use assets, and other assets			(9,224)	(7,925)
Accounts payable, accrued liabilities, and operating lease liabilities			2,565	12,486
Other liabilities			830	1,082
Net cash provided by operating activities			426,110	429,833
Additions to real estate:
Acquisitions of real estate and acquisition related capital expenditures, net of cash acquired			(458,857)	(47,585)
Redevelopment			(32,211)	(30,804)
Development acquisitions of and additions to real estate under development			(54,994)	(86,108)
Capital expenditures on rental properties			(40,013)	(41,927)
Investments in notes receivable			(6,669)	0
Collections of notes and other receivables			98,711	2,500
Proceeds from insurance for property losses			568	2,698
Proceeds from dispositions of real estate			230,935	0
Contributions to co-investments			(43,817)	(167,278)
Changes in refundable deposits			96	252
Purchases of marketable securities			(10,989)	(40,098)
Sales and maturities of marketable securities			4,301	50,226
Non-operating distributions from co-investments			25,136	26,657
Net cash used in investing activities			(287,803)	(331,467)
Cash flows from financing activities:
Proceeds from unsecured debt and mortgage notes			856,630	498,234
Payments on unsecured debt and mortgage notes			(286,074)	(473,528)
Proceeds from lines of credit			1,038,426	975,832
Repayments of lines of credit			(1,093,426)	(858,832)
Retirement of common stock			(196,404)	(56,989)
Additions to deferred charges			(7,297)	(5,873)
Payments related to debt prepayment penalties			(1,696)	0
Net proceeds from issuance of common stock			(133)	(82)
Net proceeds from stock options exercised			14,865	8,743
Payments related to tax withholding for share-based compensation			(5,664)	(3,515)
Distributions to noncontrolling interest			(15,613)	(13,842)
Redemption of noncontrolling interest			(1,703)	(14,179)
Redemption of redeemable noncontrolling interest			0	(73)
Common stock dividends paid			(264,837)	(250,686)
Net cash provided by (used in) financing activities			37,074	(194,790)
Net increase (decrease) in unrestricted and restricted cash and cash equivalents			175,381	(96,424)
Unrestricted and restricted cash and cash equivalents at beginning of period			81,094	151,395	$ 151,395
Unrestricted and restricted cash and cash equivalents at end of period	256,475	54,971	256,475	54,971	81,094
Supplemental disclosure of cash flow information:
Cash paid for interest (net of $9.0 million and $12.3 million capitalized in 2020 and 2019, respectively)			98,358	94,925
Operating cash flows from operating leases			3,430	3,392
Supplemental disclosure of noncash investing and financing activities:
Issuance of DownREIT units in connection with acquisition of real estate			0	65,472
Transfers between real estate under development and rental properties, net			131,960	138
Transfer from real estate under development to co-investments			1,473	240
Reclassifications (from) to redeemable noncontrolling interest to/from additional paid in capital and noncontrolling interest			(4,169)	1,428
Initial recognition of operating lease right-of-use assets			0	77,645
Initial recognition of operating lease liabilities			0	79,693
Debt assumed in connection with acquisition			0	98,681
Essex Portfolio, L.P.
Cash flows from operating activities:
Net income	90,076	98,061	418,841	223,566
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization			265,168	240,033
Amortization of discount on marketable securities			(4,862)	(10,869)
Amortization of discount and debt financing costs, net			3,973	1,726
Gain on sale of marketable securities			(33)	(498)
Provision for credit losses			97	0
Unrealized loss (gain) on equity securities recognized through income			1,073	(4,454)
Company's share of gain on the sales of co-investments			0	(870)
Earnings from co-investments			(38,554)	(32,365)
Operating distributions from co-investments			29,613	38,699
Accrued interest from notes and other receivables			(835)	(2,896)
Gain on the sale of real estate and land			(16,597)	0
Equity-based compensation			4,043	5,321
Loss (gain) on early retirement of debt, net	5,027	(332)	4,706	(1,668)
Gain on remeasurement of co-investment	0	0	(234,694)	(31,535)
Changes in operating assets and liabilities:
Prepaid expenses, receivables, operating lease right-of-use assets, and other assets			(9,224)	(7,925)
Accounts payable, accrued liabilities, and operating lease liabilities			2,565	12,486
Other liabilities			830	1,082
Net cash provided by operating activities			426,110	429,833
Additions to real estate:
Acquisitions of real estate and acquisition related capital expenditures, net of cash acquired			(458,857)	(47,585)
Redevelopment			(32,211)	(30,804)
Development acquisitions of and additions to real estate under development			(54,994)	(86,108)
Capital expenditures on rental properties			(40,013)	(41,927)
Investments in notes receivable			(6,669)	0
Collections of notes and other receivables			98,711	2,500
Proceeds from insurance for property losses			568	2,698
Proceeds from dispositions of real estate			230,935	0
Contributions to co-investments			(43,817)	(167,278)
Changes in refundable deposits			96	252
Purchases of marketable securities			(10,989)	(40,098)
Sales and maturities of marketable securities			4,301	50,226
Non-operating distributions from co-investments			25,136	26,657
Net cash used in investing activities			(287,803)	(331,467)
Cash flows from financing activities:
Proceeds from unsecured debt and mortgage notes			856,630	498,234
Payments on unsecured debt and mortgage notes			(286,074)	(473,528)
Proceeds from lines of credit			1,038,426	975,832
Repayments of lines of credit			(1,093,426)	(858,832)
Retirement of common stock			(196,404)	(56,989)
Additions to deferred charges			(7,297)	(5,873)
Payments related to debt prepayments penalties			(1,696)	0
Net proceeds from issuance of common stock			(133)	(82)
Net proceeds from stock options exercised			14,865	8,743
Payments related to tax withholding for share-based compensation			(5,664)	(3,515)
Distributions to noncontrolling interest			(4,152)	(3,925)
Redemption of noncontrolling interest			(1,703)	(14,179)
Redemption of redeemable noncontrolling interest			0	(73)
Common stock dividends paid			(276,298)	(260,603)
Net cash provided by (used in) financing activities			37,074	(194,790)
Net increase (decrease) in unrestricted and restricted cash and cash equivalents			175,381	(96,424)
Unrestricted and restricted cash and cash equivalents at beginning of period			81,094	151,395	151,395
Unrestricted and restricted cash and cash equivalents at end of period	$ 256,475	$ 54,971	256,475	54,971	$ 81,094
Supplemental disclosure of cash flow information:
Cash paid for interest (net of $9.0 million and $12.3 million capitalized in 2020 and 2019, respectively)			98,358	94,925
Operating cash flows from operating leases			3,430	3,392
Supplemental disclosure of noncash investing and financing activities:
Issuance of DownREIT units in connection with acquisition of real estate			0	65,472
Transfers between real estate under development and rental properties, net			131,960	138
Transfer from real estate under development to co-investments			1,473	240
Reclassifications (from) to redeemable noncontrolling interest to/from additional paid in capital and noncontrolling interest			(4,169)	1,428
Initial recognition of operating lease right-of-use assets			0	77,645
Initial recognition of operating lease liabilities			0	79,693
Debt assumed in connection with acquisition			$ 0	$ 98,681